By using electrical stimulation to bypass neurons which have become non-functional, implanted neural prostheses such as the cochlear implant have rehabilitated patients for whom there is no other treatment. The applicant proposes that a similar approach could benefit a subset of patients blind from retinitis pigmentosa and age-related macular degeneration, two leading causes of blindness. The results to date have supported this approach and show that vision compatible with mobility and large print reading is possible. The next critical step is to determine the maximum resolution affordable by such an approach. In this proposal, the applicant delineates key experiments necessary to achieve this goal.